The present invention relates generally to well tools of the type used in drilling, completing and workover of oil and gas wells and specifically to a well tool of the type which can be operated to eject a ball into a pipe string without opening the pipe string to the atmosphere.
At times during well drilling, completion, and workover activities, it becomes desirable to drop a ball into the pipe string. Any of a number of purposes may be served by dropping a ball into the pipe string. For instance, the ball can be dropped at the surface to be caught in a ball catching sub located further down the pipe string within the well bore. The then sealed-off conduit can be pressured up from the surface to provide hydraulic actuation for gripping and sealing elements carried on the pipe string. Balls are also used in cementing operations to divert the flow of cement where staged cementing operations are employed. The ball can also be dropped to allow a pin to be sheared as a part of the operating procedure for a given well tool.
A variety of devices are shown in the prior art for dropping one or more balls into a fluid conduit to clean the interior surfaces of a production pipe line. Other known devices allow a plurality of balls to be introduced into the stream of treating fluid being pumped down the well, such as during perforation sealing operations. Devices have also been provided on pipe strings for injecting one or more balls into the string to act as well safety valves. Such devices provided ball release in response to hazardous conditions such as fire. Each of the above mentioned devices were complicated in design and involved a multitude of intricately machined parts, springs, valves, and the like. Such devices were not well suited for the purpose of insertion in the pipe string above the rig floor for injecting a single ball into the well string.
As a result, in the past when it was desired to drop a single large diameter ball into the pipe string to be caught in a ball dropping sub, or the like, the pipe string joint at the rig floor was broken out and a ball was manually inserted in the pipe string. The pipe string joint was then again made up and work continued. The disadvantage of such a technique was the wasted time involved in breaking out and making up the pipe joint. Also, if fluids were being run through the pipe string under pressure, operations were shut down while the joint was broken out.
There has existed a need, therefore, for a simple device for insertion in a string of pipe which could be operated at the rig floor to drop a ball into the pipe string without the necessity of opening the assembly to the atmosphere.